Answers

Nothing flowers for long in the shrub and tree department - a month if you're lucky, a couple of weeks more usually. Which is why its best to choose shrubs and trees because of the way they look for the other 48/50 weeks of the year, because that's what you'll be looking at most of the time.

bamboo is right . theres a plant called a day lilly which somes that up . they just have to be polynated which takes one or two insects job done . i believe what the chinese do is get different veriaties of cherry that flower at slightly different times giving the impression of long flowering . you can reproduce this idea with other plants that flower at different times but as already said you should treat the flowers as a bonus on a plant you love anyway . if you want to experiment pick a blossom and put a bit of coloured tape round its base then youl see just how short lived they are .

I'd choose an Amelanchier - blossom in spring, purplish tints to the leaves when they first open, turning green, berries later on and good autumn reds just before the leaves drop. Also often multistemmed rather than single stem, make interesting outlines in winter, specially with snow on them, so at least 3 seasons of interest. Amelanchier lamarckii gets about 33 feet at maturity - for a smaller one, A. 'Ballerina' only gets about 13 feet.

Oh i love the ballerina, think i needvsomething smaller though, once it got to full height it would allow easy access to my garden for any wee horrors trying to scale the fence! Aything similar that goes to maybe 6 foot ish

I don't think it would allow easy access - the branches won't be anything like strong enough for people to use to climb onto, particularly the top ones, unlike a tree. A prunus there (cherry tree) might well provide such support for invaders though...
If you want to keep people out, plant a pyracantha - not so attractive, and prefers to be against a fence or wall, but it does give berries in autumn, does have flattish heads of blossom in May and is devilishly thorny...